Method of manufacturing thin-film magnetic head

ABSTRACT

A method of manufacturing a thin-film magnetic head, includes the steps of: forming, on a lower auxiliary pole, a three-layer pole tip structure consisting of a lower pole tip element, a recording gap layer and an upper pole tip element; depositing a lower insulating layer on the three-layer pole tip structure; polishing the lower insulating layer by chemical-mechanical polishing so that a top surface of the lower insulating layer is leveled lower than a top of the three-layer pole tip structure over at least a region within which a coil conductor is formed; forming the coil conductor on the lower insulating layer; forming an upper insulating to cover the coil conductor; and forming an upper auxiliary pole so that a part of which contacts to the upper pole tip element.

This is a Division of Application No. 09/150,205 filed Sep. 9. 1998, nowU.S. Pat. No. 6,169,642. The disclosure of the prior application(s) ishereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a thin-film magnetic head provided withat least an inductive recording transducer element and a method ofmanufacturing the head.

DESCRIPTION OF THE RELATED ART

Recently, demand for higher recording density has made a recording trackwidth narrower, and therefore a submicron width of the pole of therecording head part has been needed. To cope with such narrower polewidth, a thin-film magnetic head is formed in a manner that only therecording pole portion is separated from other portions. That is, athree-layer pole tip structure with a lower pole tip element, arecording gap layer and an upper pole tip element is formed at only apole tip region located between an air bearing surface (ABS) and aposition at a predetermined height from the ABS in the recording headpart, and an upper yoke and a lower yoke are magnetically connected tothe top surface and the bottom surface of this pole tip structure,respectively.

FIG. 1 is a schematic ABS view, illustrating an example of aconventional composite type thin-film magnetic head with an inductiverecording head part and a magnetoresistive (MR) reproducing head part.

In the figure, the reference numeral 10 denotes a lower shield layer ofthe MR reproducing head part, 11 denotes an upper shield layer of the MRhead part, which also acts as a lower auxiliary pole of an inductiverecording head part, 12 denotes a MR layer provided through aninsulating layer 13 between the lower shield layer 10 and the uppershield layer 11, 14 denotes a lower pole tip element of the inductiverecording head part, 15 denotes an upper pole tip element, 16 denotes arecording gap layer formed between the lower and upper pole tip elements14 and 15, 17 denotes an insulating layer deposited on the upper shieldlayer 11 and around a three-layer pole tip structure consisting of thelower pole tip element 14, the recording gap layer 16 and the upper poletip element 15, and 18 denotes an upper auxiliary pole formed on theinsulating layer 17 and deposited to contact with the upper pole tipelement 15. The upper auxiliary pole 18 is magnetically connected withthe lower auxiliary pole (upper shield layer) 11 at its rear portion soas to constitute a magnetic yoke together with the lower auxiliary pole11.

The head with the three-layer pole tip structure shown in FIG. 1 canrealize a narrower track width. However, peeling is liable to occur atthe interface between the upper pole tip element 15 and the upperauxiliary pole 18 which are located at the trailing side and act animportant role during recording. Also, since the three-layer polestructure has a narrow pole width of submicron, the magnetic domain,i.e. the easy magnetization axis, directs to a longitudinal direction ofthe poles causing the recording current to magnetic field conversionefficiency to lower.

FIG. 2 is a schematic ABS view illustrating another example of aconventional composite type thin-film magnetic head having a three-layerpole structure, described in U.S. Pat. No. 5,452,164, and FIG. 3 is across-sectional view perpendicular to the plane of the ABS, illustratingthe example of FIG. 2.

In FIG. 2, the reference numeral 20 denotes a lower shield layer of theMR reproducing head part, 21 denotes an upper shield layer of the MRhead part, which also acts as a lower auxiliary pole of an inductiverecording head part, 22 denotes a MR layer provided through aninsulating layer 23 between the lower shield layer 20 and the uppershield layer 21, 24 denotes a lower pole tip element of the inductiverecording head part, 25 denotes an upper pole tip element, 26 denotes arecording gap layer formed between the lower and upper pole tip elements24 and 25, 27 denotes a lower insulating layer deposited on the uppershield layer 21 and around a three-layer pole structure consisting ofthe lower pole tip element 24, the recording gap layer 26 and the upperpole tip element 25, 28 denotes an upper auxiliary pole, 29 denotes acoil conductor formed on the lower insulating layer 27, and 30 denotesan upper insulating layer covering the coil conductor 29, respectively.In this example, the three-layer pole tip structure protrudes from theupper surface of the lower insulating layer 27 at a region near the ABS.The upper auxiliary pole 28 is formed to cover the protruded portion ofthe upper pole tip element 25 of the pole tip structure. This upperauxiliary pole 28 is magnetically connected with the lower auxiliarypole (upper shield layer) 21 at its rear portion so as to constitute amagnetic yoke together with the lower auxiliary pole 21.

However, according to the conventional structure shown in FIGS. 2 and 3,the top of the lower insulating layer 27 at a region on which the coilconductor 29 is formed, which is far from the ABS, is formed so that itis certainly higher than the top of the three-layer pole tip structure.Thus, it is difficult to efficiently release heat generated by therecording current flowing through the coil conductor 29. In general, itis necessary that heat from the coil conductor 29 is released outwardvia a metal member to enhance the reliability of the magnetic head.However, because the upper auxiliary pole 28 has small volume, it isinsufficient to radiate the heat. In addition, because the lowerinsulating layer 27 is thick at this region under the upper auxiliarypole 28, it is difficult to efficiently transmit the heat to the uppershield layer 21.

Furthermore, because of the aforementioned conventional structure inwhich height in the top of the upper pole tip element 15 is the same asthat of the insulating layer 17, peeling often occurs at the interfacebetween the upper pole tip element 15 and the upper auxiliary pole 18.

Also, the conventional method for manufacturing the three-layer pole tipstructure shown in FIGS. 2 and 3 causes its fabricating processes to bevery complicated.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide athin-film magnetic head and a method of manufacturing the head, wherebydecrease in reliability derived from generation of heat can beeffectively prevented.

Another object of the present invention is to provide a thin-filmmagnetic head and a method of manufacturing the head, whereby peeling atthe interface between the upper pole tip element and the upper auxiliarypole can be prevented.

Further object of the present invention is to provide a thin-filmmagnetic head and a method of manufacturing the head, wherebymanufacturing processes can be simplified.

According to the present invention, a thin-film magnetic head having anair bearing surface, includes a three-layer pole tip structureconsisting of a lower pole tip element, a recording gap layer and anupper pole tip element, the structure having side surfaces, a rearsurface and top surface, a lower auxiliary pole, a part of whichcontacts to the lower pole tip element, an upper auxiliary pole, a partof which contacts to the upper pole tip element, the upper auxiliarypole being magnetically connected at its rear portion with respect tothe air bearing surface to the lower auxiliary pole so as to form a yoketogether with the lower auxiliary pole, a lower insulating layer,surrounding the side surfaces and the rear surfaces of the three-layerpole tip structure, the lower insulating layer being located between thelower and upper auxiliary poles and having a top surface, a coilconductor formed on the top surface of the lower insulating layer, andan upper insulating layer covering the coil conductor, a part of theupper insulating layer being located between the lower insulating layerand the upper auxiliary pole. The top surface of the lower insulatinglayer is leveled lower than the top surface of the three-layer pole tipstructure over at least a region within which the coil conductor isformed.

Since the top surface of the lower insulating layer on which the coilconductor is formed is constructed in a level lower than the top surfaceof the upper pole tip element, the lower insulating layer itself can bemade as a thin layer. As a result, heat generated from the coilconductor can be easily transmitted to the lower auxiliary pole arrangedbelow the coil conductor. In particular, since the lower auxiliary polehas a large area and the lower insulating layer is made thin, the heatdispersion effects are increased, whereby generation of heat from amagnetic head can be effectively prevented.

It is preferred that the top surface of the lower insulating layer isformed in flat over its entire surface.

It is also preferred that the top surface of the lower insulating layeris leveled lower than the top surface of the three-layer pole tipstructure over its entire surface.

It is preferred that a part of the upper pole tip element is protrudedfrom the top surface of the lower insulating layer, and that the upperauxiliary pole is fixed to the part of the upper pole tip element so asto cover the part of the protruded upper pole tip element.

It is also preferred that a level difference between the top surface ofthe lower insulating layer adjacent to the three-layer pole tipstructure and the top of the three-layer pole tip structure is 25 nm ormore.

Preferably, the thin-film magnetic head is a composite type thin-filmmagnetic head with a MR reproducing head part having a lower shieldlayer, an upper shield layer and a MR layer formed between the lower andupper shield layers through an insulating layer, and the upper shieldlayer also acts as the lower auxiliary pole.

According to the present invention, also, a method of manufacturing athin-film magnetic head includes the step of forming, on a lowerauxiliary pole, a three-layer pole tip structure consisting of a lowerpole tip element, a recording gap layer and an upper pole tip element,the step of depositing a lower insulating layer on the three-layer poletip structure, the step of polishing the lower insulating layer bychemical-mechanical polishing (CMP) so that a top surface of the lowerinsulating layer is leveled lower than a top of the three-layer pole tipstructure over at least a region within which a coil conductor isformed, the step of forming the coil conductor on the lower insulatinglayer, the step of forming an upper insulating layer to cover the coilconductor, and the step of forming an upper auxiliary pole so that apart of which contacts to the upper pole tip element.

After forming the lower insulating layer on a three-layer pole tipstructure, this lower insulating layer is polished by a CMP process sothat the top surface of the lower insulating layer is in a level lowerthan the top surface of the three-layer pole tip structure (the topsurface of the upper pole tip element) over at least a region withinwhich a coil conductor is formed. Thus, by only polishing using CMPprocess, the upper pole tip element of the three-layer pole tipstructure is upward protruded from the lower insulating layer and thetop surface of the lower insulating layer is in a level lower than thetop surface of the three-layer pole tip structure over at least a regionwithin which a coil conductor is formed, causing the manufacturingprocesses to be very simplified.

It is preferred that the polishing step includes the step of polishingso that the top surface of the lower insulating layer is formed in flatover its entire surface.

It is also preferred that the polishing step includes the step ofpolishing so that the top surface of the lower insulating layer isleveled lower than the top surface of the three-layer pole tip structureover its entire surface.

It is preferred that the polishing step includes the step of polishingso that a part of the upper pole tip element is protruded from the topsurface of the lower insulating layer, and that the upper auxiliary poleforming step includes the step of forming the upper auxiliary pole tofix to the part of the upper pole tip element so as to cover the part ofthe protruded upper pole tip element.

Preferably, the method further includes the step of forming a lowershield layer, the step of forming a MR layer on the lower shield layer,and the step of forming an upper shield layer on the MR layer through aninsulating layer, the upper shield layer acting also as the lowerauxiliary pole.

Further objects and advantages of the present invention will be apparentfrom the following description of the preferred embodiments of theinvention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic ABS view of the already described example of theconventional composite type thin-film magnetic head having a three-layerpole tip structure;

FIG. 2 is a schematic ABS view of the already described another exampleof the conventional composite type thin-film magnetic head having athree-layer pole tip structure;

FIG. 3 is a cross-sectional view of the example of FIG. 2, perpendicularto the plane of the ABS;

FIG. 4 is a schematic ABS view of a preferred embodiment of a compositetype thin-film magnetic head having an inductive recording head part anda MR reproducing head part according to the present invention;

FIG. 5 is a cross-sectional view of the magnetic head of FIG. 4,perpendicular to the plane of the ABS;

FIG. 6 is an exploded oblique view of the magnetic head of FIG. 4; and

FIGS. 7 to 16 are schematic illustrations of a sequence of processes inthe manufacturing method of the thin-film magnetic head according to thepresent invention; and

FIGS. 17 to 19 are schematic illustrations of another sequence ofprocesses in the manufacturing method of the thin-film magnetic headaccording to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 4 to 6 illustrate a preferred embodiment of a composite typethin-film magnetic head having an inductive recording head part and a MRreproducing head part according to the present invention. FIG. 4 is aschematic ABS view, FIG. 5 is a cross-sectional view perpendicular tothe plane of the ABS, and FIG. 6 is an exploded oblique view.

In these figures, the reference numeral 40 denotes a lower shield layerfor the MR reproducing head part, 41 denotes an upper shield layer, 42denotes a MR layer formed between the lower and upper shield layers 40and 41 through an insulating layer 43, 44 denotes a lower pole tipelement of the inductive recording head part, 45 denotes an upper poletip element, 46 denotes a recording gap layer formed between the lowerand upper pole tip elements 44 and 45, and 47 denotes a lower insulatinglayer deposited on the upper shield layer 41 and around a three-layerpole tip structure consisting of the lower pole tip element 44, therecording gap layer 46 and the upper pole tip element 45. Furthermore,in the figures, the reference numeral 48 denotes an upper auxiliarypole, 49 denotes a coil conductor formed on the lower insulating layer47, and 50 denotes an upper insulating layer deposited so as to coverthe coil conductor 49, respectively. The upper shield layer 41 contactsto the lower pole tip element 44 to act as a lower auxiliary pole. Theupper auxiliary pole 48 is magnetically connected with the lowerauxiliary pole (upper shield layer) 41 at its rear portion so as toconstitute a magnetic yoke together with the lower auxiliary pole 41.

In this embodiment, the top (upper surface) of the lower insulatinglayer 47 from the side of the upper pole tip element 45 to a regionwherein the coil conductor 49 is formed is made flat, and thethree-layer pole tip structure consisting of the lower pole tip element44, the recording gap layer 46 and the upper pole tip element 45 isupward protruded from this flat top of the lower insulating layer 47.Namely, since the top of the lower insulating layer 47 on which the coilconductor 49 is formed is leveled, over its entire region, lower thanthe top of the upper pole tip element 45, the layer thickness of thislower insulating layer 47 can be thinner. As a result, heat generatedfrom the coil conductor 49 can be easily transmitted to the upper shieldlayer (lower auxiliary pole) 41 through the insulating layer 47. Inparticular, since the upper shield layer 41 has a large area, the heatdispersion effects increases by making the lower insulating layer 47thin, whereby generation of heat from the magnetic head can beeffectively prevented.

Protruded height H of the upper pole tip element 45 from the top of thelower insulating layer 47 is 5 nm or more (H≧5 nm). The upper auxiliarypole 48 is formed to envelop the protruded portion of the upper pole tipelement 45. Keeping of the protruded height as H≧5 nm will result thecontact area between the upper pole tip element 45 and the upperauxiliary pole 48 to sufficiently increase, thereby enhancing adhesionand reducing peeling at the interface therebetween. Thus, according tothe present invention, the product yield can be improced. The protrudedheight is, in considering the patterning process, preferably H=25 to 250nm. Table 1 shows incidence of peeling failure depending upon theprotruded height of the upper pole tip element 45 from the top of thelower insulating layer 47.

TABLE 1 PROTRUDED INCIDENCE OF HEIGHT H (nm) PEELING FAILURE (%) 0 67.805 9.30 25 0.61 53 0.06 250 0.00 1400 0.00

In addition, according to the present invention, since magnetic couplingbetween the upper pole tip element 45 and the upper auxiliary pole 48 isstrengthened, it is prevented that the magnetic domain (axis of easymagnetization) of the three-layer pole tip structure directs to alongitudinal direction of the pole. As a result, efficiency of recordingcurrent to magnetic field conversion can be maintained at a high level.

FIGS. 7 to 16 schematically illustrate a sequence of processes in themanufacturing method of the aforementioned composite type thin-filmmagnetic head according to the present invention.

As shown in FIG. 7, on a substrate or wafer (not shown), a MRreproducing head part with the lower shield layer 40, the MR layer, theinsulating layer 43 and the upper shield layer 41 is first formed. Afterthat, on the upper shield layer 41, a magnetic layer 70 for the lowerpole tip element 44, an insulating layer 71 for the recording gap layer46 and a recording layer 72 for the upper pole tip element 45 in theinductive recording head part are sequentially deposited.

In this embodiment, as the upper shield layer 41, about 3.5 μm thickNiFe (80 wt % Ni−20 wt % Fe) is formed by electroplating. As the lowerand upper pole tip elements 44 and 45, the layers 70 and 72 made of ahigh Bs material such as FeZrN or FeN are deposited by sputtering tohave a thickness of about 0.5 μm. In place of the high Bs material, NiFemay be used. As the recording gap layer 46, the insulating layer 71 madeof an insulating material such as SiO₂ is deposited by sputtering tohave a thickness of about 0.3 μm.

These three layers constituting the pole tip structure can be depositedin the same chamber. The sputtering conditions of each layer is shown inTable 2.

TABLE 2 FeZrN SiO₂ RF/DC DC RF APPLIED POWER (kW) 1.40 0.90 SPUTTERINGPRESSURE (Pa) 0.20 1.00 SPUTTERING RATE (nm/min) 11 2 DISTANCE BETWEENELECTRODES (mm) 130 130

Then, as shown in FIG. 8, a resist frame 73 having an openingcorresponding to a portion of a mask (74 shown in FIG. 9) to be formedis formed on the magnetic layer 72 for the upper pole tip element 45.The opening has a width of about 0.3 to 2.0 μm. In this embodiment, asthe resist frame 73, a novolak type resist layer having a thickness ofabout 2 to 5 μm is deposited and then patterned by a photolithographytechnique.

The mask 74 is then formed by electroless plating as shown in FIG. 9. Itis desirable that before electroless plating, the wafer is immersed in4.5% HCl solution for 1.5 min to obtain wetting properties of theplating surface.

The plated mask 74 is a metal compound composed of a base material ofnickel (Ni) metal and cobalt (Co) metal, and additives of 3B groupelement such as boron (B) and 5B group element such as phosphorus (P).The thickness of the mask 74 is about 1.0 to 3.0 μm.

The resist frame 73 is then removed with acetone remover therebyobtaining a structure shown in FIG. 10.

Then, the three layers 70, 71 and 72 are etched by ion milling using themask 74 as shown in FIG. 11. The ion milling conditions are, forexample, an accelerating voltage of 500 mV and an accelerating currentof 400 mA. By this ion milling, the magnetic layer 70, insulating layer71 and magnetic layer 72 except for an area below the mask 74 areremoved to form the lower pole tip element 44, recording gap layer 46and upper pole tip element 45 as shown in FIG. 12.

Then, the mask 74 is removed by means of some removing technique toprovide a patterned three-layer pole structure consisting of the lowerpole tip element 44, the recording gap layer 46 and the upper pole tipelement 45, as shown in FIG. 13.

Then, as shown in FIG. 14, an insulating layer 75 consisting of aninsulating material such as Al₂O₃ or SiO₂ is deposited by sputtering.The thickness of the insulating layer 75 is determined to a value suchthat the top of the three-layer pole tip structure formed by ion millingis fully buried in this layer 75, for example about 0.5 to 15 μm.

After depositing the insulating layer 75, this layer 75 is polished by aCMP process to expose the upper pole tip element 45, as shown in FIG.15. The CMP in this embodiment is carried out using oxide abrasiongrains such as Al₂O₃ or SiO₂, having each diameter of about 0.02 to 0.3μm and alkaline slurry using KOH as additives. As a polishing pad, asynthetic fiber type such as urethane is used.

Even after the upper pole tip element 45 has been exposed, the polishingis still continued so that only the insulating layer 75 is selectivelypolished to flatten the top of the layer 75 and that the top portion ofonly a required height H of the upper pole tip element 45 is exposedfrom the top of the lower insulating layer 47, by suitably selectingconditions of the CMP process, such as pH, grain size etc.Alternatively, after exposing the upper pole tip element 45 by a CMPpolishing process, the insulating layer 75 may be etched so that the topportion of only a required height H of the upper pole tip element 45 isexposed from the top of the lower insulating layer 47. However, thenumber of steps is increased in the latter case. In the etching process,an etchant such as NaOH by which only the insulating layer 75 will befurther selectively etched than the upper pole tip element 45 is used.As mentioned above, by executing the CMP process, the top of theinsulating layer 75 is flatted over a region located between the side ofthe upper pole tip element 45 and a position on which the coil conductor49 is formed to form the lower insulating layer 47.

Then, as shown in FIG. 5, on the lower insulating layer 47 is formed thecoil conductor 49 on which the upper insulating layer 50 is deposited.This upper insulating layer 50 is formed by depositing a novolak typephotoresist and by patterning using a photolithography technique. InFIG. 5, the insulating layer 50 is formed so that its tip end of the ABSside is terminated at a position spaced from the rear end of the upperpole tip element 45. However, this layer 50 may be formed so that itstip end of the ABS side is terminated at the rear end of the upper poletip element 45, or that its tip end of the ABS side covers at least apart of the upper pole tip element 45.

Then, as shown in FIG. 16, after forming a resist frame by aphotolithography technique, the upper auxiliary pole 48 is formed byelectroplating. This upper auxiliary pole 48 is formed so that itenvelops a protruded portion of the upper pole tip element 45. Also, theupper auxiliary pole 48 is magnetically connected to the upper shieldlayer 41 at the rear portion so as to form a yoke. By theabove-mentioned processes, the thin-film magnetic head having thecross-sectional view of FIG. 5 can be obtained.

FIGS. 17 to 19 schematically illustrate another sequence of processes inthe manufacturing method of the aforementioned composite type thin-filmmagnetic head according to the present invention.

As shown in FIG. 17, on a substrate or wafer (not shown), a MRreproducing head part is first formed. After that, on the upper shieldlayer 41, a resist frame 76 having an opening corresponding to a portionof the three-layer pole tip structure to be formed is formed. Theopening has a width of about 0.3 to 2.0 μm. In this embodiment, as theresist frame 76, a novolak type resist layer having a thickness of about2 to 5 μm is deposited and then patterned by a photolithographytechnique. Kind of the resist material and its thickness may beadequately selected in accordance with the width of the opening.

In this embodiment, also, the upper shield layer 40 is formed by amaterial such as NiFe (80 wt % Ni−20 wt % Fe) by using aphotolithography technique and an electroplating process to have athickness of about 3.5 μm.

Then, as shown in FIG. 18, the three-layer pole tip structure is formedby sequentially plating the lower pole tip element 44, the recording gaplayer 46 and upper pole tip element 45. As the lower pole tip element44, an about 0.5 μm thick NiFe series alloy thin-film is formed byelectroplating. As the recording gap layer 46, a non-magnetic Ni seriesalloy thin-film is formed by electroless plating. The bath temperatureand pH of the bath at electroless plating are 55° C. and 6.0 to 6.5,respectively. As the upper pole tip element 45, an about 0.5 μm thickNiFe series alloy thin-film is formed by electroplating as well as thelower pole tip element 44.

Then, by removing the resist frame using a remover such as acetone thepatterned three-layer pole tip structure consisting of the lower poletip element 44, recording gap layer 46 and upper pole tip element 45 isformed as shown in FIG. 19.

The following processes are the same as those of the former embodiment,shown in FIGS. 14 to 16.

Many widely different embodiments of the present invention may beconstructed without departing from the spirit and scope of the presentinvention. It should be understood that the present invention is notlimited to the specific embodiments described in the specification,except as defined in the appended claims.

What is claimed is:
 1. A method of manufacturing a thin-film magnetichead, comprising the steps of: forming, on a lower auxiliary pole, athree-layer pole tip structure consisting of a lower pole tip element, arecording gap layer and an upper pole tip element; depositing a lowerinsulating layer on said three-layer pole tip structure such that thetop of the three-layer pole tip structure is fully buried by said lowerinsulating layer; polishing said lower insulating layer bychemical-mechanical polishing so that a top surface of said lowerinsulating layer is leveled lower than the top of said three-layer poletip structure over a least a region within which a coil conductor is tobe formed; forming the coil conductor on said lower insulating layer;forming an upper insulating layer to cover said coil conductor; andforming an upper auxiliary pole so that a part of which contacts to saidupper pole tip element.
 2. The method as claimed in claim 1, whereinsaid polishing step includes the step of polishing so that the topsurface of said lower insulating layer is formed in flat over its entiresurface.
 3. The method as claimed in claim 1, wherein said polishingstep includes the step of polishing so that the top surface of saidlower insulating layer is leveled lower than the top surface of saidthree-layer pole tip structure over its entire surface.
 4. The method asclaimed in claim 1, wherein said polishing step includes the step ofpolishing so that a part of said upper pole tip element is protrudedfrom the top surface of said lower insulating layer, and wherein saidupper auxiliary pole forming step includes the step of forming the upperauxiliary pole to fix to and cover the part of said upper pole tipelement that is protruded from the top surface of said lower insulatinglayer.
 5. The method as claimed in claim 1, wherein said method furthercomprises the step of forming a lower shield layer, the step of forminga magnetoresistive layer on said lower shield layer, and the step offorming an upper shield layer on said magnetoresistive layer through aninsulating layer, said upper shield layer acting also as the lowerauxiliary pole.